Protective helmet



Oct. 6, 1942. J. T. CLARK PROTECTIVE HELMET Filed July 15. 1940 PatentedOct. 6, 1942 PROTECTIVE HELMET .lohn T. Clark, Cicero, Ill., assigner toJohn T. Clark Company, a corporation of Illinois Application July 15,1940, Serial No. 345,656

2 Claims.

This invention relates to a protective helmet, and particularly to oneformed from a unitary skull shaped plate of hard resilient waterproofmaterial.

There has been for some time a considerable demand for a protectivehelmet of resilient waterproof material of great strength. Helmets ofthis type are necessary in football, polo, and certain other strenuoussports, and also in many occupations, such, for example, as for the crewof a tank, racing drivers, army aviators, or in any other occupationwhere the head is likely to be brought into violent contact with anyhard object.

The helmets now in use are either leather or similar pads or are builtup from a combination of fibrous material or fibre board in combinationwith other parts such as lining, cover, etc. All of the materials nowemployed for this purpose are extremely susceptible to water, eitherfrom outside the helmet or water generated by perspiration inside thehelmet, and once wet, lose their effectiveness as well as becomingheavy, cold and clammy. At the same time none of the protective devicesnow on the market having any strength can be made in a single piece,and'none of them have the shock, impact cr wear resistance desirable ina helmet.

In accordance with the present invention a helmet is prepared which iscompletely waterproof, which may be prepared in a single piece, whichhas tensile strength, impact resistance and wear resistance farexceeding anything heretofore on the market, but which is stillresilient.

A helmet prepared in accordance with the invention and constructedespecially for football is illustrated somewhat diagrammatically in thedrawing. It comprises an integral skull shaped plate I which is enlargedat its lower extremities into two lobes II and I2 to provide room forthe ears. These lobes are pierced at the proper points with one or moreopenings I3. A lining I4 of any suitable material, such as paddedleather, may be placed inside the lower portion of the helmet. It is oneof the advantages of the material here employed that it can readily bestitched in this manner. A plurality of ventilating openings I6 arepreferably incorporated in the top of the helmet and around the sides.The usual `pad I'I., held away from the crown of the -helmet by theelastics I8, is preferably `incorporated to avoid direct contact of theskull and the helmet.

If desired, the helmet may be reinforced by a metal skull shaped sheetsweated inside the plate I0 or between two plates I0 in the mannerhereinafter described.

vThe integral plate Ill is composed of a molded composition which isformedon a mold while hot for this purpose is a mixture consistingessentially of thermoplastic rubber and ordinary natural or syntheticrubber. The proportions of thermoplastic and natural rubber must becarefully adjusted. The preferred material is prepared from 4.5 lbs. ofpale crepe rubber, 6.5 lbs. of a thermoplastic rubber such as theproduct now prepared by the du Pont Company and known as Isolac which isprepared in accordance with the disclosure of Williams Patent 2,158,530,1.5 lbs. of zinc oxide which is used as a filler, 2 lbs. of Whitingemployed for the same purpose, and small amounts of sulphur and suitablevulcanizing accelerators and retarders. In combination with the aboveformula, it is preferred to use 2 oz. of stearic acid, 3 oz. of theaccelerator Zenite A, 1 oz. of diorthothioguanadine, 0.8 oz. of RetarderW, 4.25 oz. of sulphur, and 1.2 oz. of an antiaging material such asthat known as Antox. The amounts of filler may be varied considerably inthe above combination. The vulcanizing ingredients used may be varied tosuit the individual requirements or the particular rubber employed.

The ratio of thermoplastic and natural rubber, however, should be heldwithin close limits. A formula in which 8 lbs. of thermoplastic rubberand 4 lbs. of normal rubber are employed produces a plate which isextremely hard and is about the limit to which the proportion ofthermoplastic rubber can be increased.

On the other hand, a combination in which 5 lbs. of normal rubber and5.75 lbs. of thermoplastic rubber is used, is about as soft a product aswill provide protective value under normal circumstances.

In the following formulae, formula A represents the preferred form;formula B, the approximate maximum ratio of thermoplastic to naturalrubber; and formula C, the approximate minimum ratio of thermoplastic tonormal rubber.

A B C Lbs. Oz. Lbs. 02. Lbs. 02. Pale crepe 4.5 0 4 0 5 0 Isolac 0 8 0 575 0 Zinc oxide" 0 2. 5 0 0 l2 2 0 2 0 2 0 l 0 4 0 0 8 It will be notedthat in the above formulae the amount of filler is increasedconsiderably ln the softer composition C, which partially offsets thedrop in quantity of thermoplastic rubber.

, Football helmets prepared in accordance with the above formulae showmost remarkable properties. In the following tables are shown thetensile strength, elongation, breaking load, and yield point of portionscut from the material with a dumbbell die measuring 0.25 inch' at itsnarrowest point, which were subjected to the tests..

Tensile Elonga- Breaking Yield strength tion load point Pounds PercentPounds Pounds Averages Pounds Percent Pounds` Pounds Pounds PercentPounds Pounds Averages Pounds Percent Pounds Pounds 2066.9 275 119.0119.0

Pounds Percent Pounds Pounds Averages Pounds Percent Pounds Pounds Apenetration test made by dropping a needle with the weight of 150 gramsa distance of one inch was made on the three samples With the followingresults:

Sample A Sample B Sample C Millimeters Millimeters Millimeters AveragePenetration lilillz'meter.o Millimeters Millimeter-s l. 22 l. 26 1. 46

Bending test First bend Second Angle bend In forming the helmet, thematerials in the formula are mixed together and vulcanized upon a moldof appropriate size and shape. The material must then be cooled upon amold, butv it has been discovered that after vulcanization is complete,the skull shaped plate may be removed from the forming mold andpermitted to shrink to size upon vvarious sized molds. For example, aforming mold of size 7% may be utilized with a plurality of coolingmolds of that size and smaller, down to and including, for example, a71A size. The ultimate size of the helmet will be determined by the sizeof the cooling mold employed. This makes it possible to produce thearticles very much more cheaply than otherwise would be ythe case, sincehelmets of all usual sizes can be produced by utilizing forming molds ofonly two sizes, for example, 'l5/8 and '7%. In this manner, it is alsopossible to sweat a metal plate inside the formed helmet by placing themetal plate over the cooling die and permitting the rubbery material toshrink into size about it. Furthermore, the helmet so formed may beprovided with a second layer of the rubbery material so that the steelor other metal plate is completely surrounded by resilient material.

The completed plate will ordinarily have a thickness between about leand Tse inch, with approximately preferred. 'Ihfe tensile strength ofthe plate, yfor a thickness of approximately ya-2 inch, should bebetween 1,250 and 2,500 lbs., the elongation between 250 and 600% andthe yield point at least 70 lbs.

As described in the Williams Patent 2,153,530, the thermoplastic rubbermay be .prepared 'by mixing natural rubber with a monohydric phenol anda catalyst, and heating. The resulting material is a rubber isomer whichis very brittle at room temperatures. The preferred material is brown incolor and has a softening point of approximately 140 F.

The foregoing detailed description has been given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom.

What I claim as new, and desire to secure by Letters Patent, is:

1. A helmet including a skull shaped plate containing as its essentialbinding element a Vulcanized mixture of 1 to 2 parts of thermoplasticrubber and 1 part of rubber.

2. A protective device comprising an integral skull-shaped plate havinga tensile strength between 1250 and 2500 lbs., an elongation between250% and 600%, and a yield point of at least 70 lbs., said plateconsisting essentially of a vulcanized plastic prepared by intimateadmixture of thermoplastic rubber and rubber in the proportions of 1 to2 parts of thermoplastic rubber to one of rubber, and including smallproportions of filler and vulcanizing ingredients.

J OHN T. CLARK.

